Over time, cellular technologies have improved significantly. A new generation of cellular standards has appeared approximately every tenth year since first generation (1G) systems were introduced in the early eighties. Each generation is characterized by new frequency bands, higher data rates and non-backward-compatible transmission technology. 2G and 2.5G networks supplanted 1G networks, and were eventually replaced by 3G technology. 4G succeeded 3G, but will soon be joined by 5G networks and devices, work on which began in 2016. 5G networks will now include operation at 20-100 GHz frequencies in what are commonly known as the millimeter wave (mmW) band of spectrum, so that 5G networks will now operate at wave frequencies between 600 MHz and 100 GHz. Radio waves in the mmW band have wavelengths from one to ten millimeters, which is much shorter than wavelengths utilized in previous generations.
New challenges come with a transition to mmW technology, as at mmW frequencies, signal absorption rates are much higher due to the higher frequencies' vulnerability to buildings, foliage, automobiles, people, gases, rain, etc. As a result, mmWaves can only transmit for short distances. To compensate, directional transmission/reception (“beamforming”) is utilized to boost gain. Beamforming identifies the most efficient data delivery route to a device and reduces interference for nearby devices. Beamforming requires that cellular transmitters and receivers be optimized for many characteristics, among them beam switching, which is required as a mobile cellular device moves in and out of distinct radio beams. Testing setups are needed for beam characterization and for checking beam acquisition, beam tracking, and beam switching performance.